1. Field of the Invention
This invention relates to a paper feeder or an image forming apparatus comprising:
a paper feed tray attachable to a tray receiver of a main apparatus body by moving in a tray moving direction perpendicular to a direction of feeding paper loaded in the feed tray; and
a tray positioning mechanism for contacting one of the paper feed tray and the main apparatus body as the paper feed tray is attached to the tray receiver, to restrict movement in an attaching direction of the paper fixed tray, the tray positioning mechanism being attached to the other of the paper feed tray and the main apparatus body;
the tray positioning mechanism having a contact portion for contacting one of the paper feed tray and the main apparatus body, a position of the contact portion being adjustable in the tray moving direction;
2. Prior Art
Such a paper feeder for an image forming apparatus (which may be referred to simply as a paper feeder hereinafter) is used in an image forming apparatus such as a copying machine, printer or facsimile machine for feeding paper one sheet at a time for forming images at an image forming station.
To describe this further, a tray positioning mechanism is allowed to contact one of a paper feed tray and a main apparatus body as the paper feed tray is moved toward a tray receiver along a tray moving direction perpendicular to a direction of feeding paper loaded in the feed tray. The tray positioning mechanism is attached to the other of the paper feed tray and the main apparatus body. This restricts movement in the attaching direction of the paper feed tray is regulated, whereby the paper feed tray is loaded into the tray receiver as positioned in the tray moving direction.
Paper is fed from the paper feed tray loaded into the tray receiver in this way, and transported to the image formation station. However, the loading position of the paper feed tray in the tray receiver is variable in the tray moving direction due to a manufacture error of the tray receiver in the main apparatus body, a manufacture error of the paper feed tray, and so on Consequently, at the image forming station, a paper setting position where the paper from the paper feed tray is placed deviates from an image forming position in a direction extending along the tray moving direction.
Then, the position of a contact portion of the tray positioning mechanism that contacts the main apparatus body or the paper feed tray is made adjustable in the tray moving direction. The position of the contact portion is adjusted along the tray moving direction to adjust the loading position of the paper feed tray to the tray receiver in the tray moving direction. By doing so, what is called optical aids adjustment is effected to adjust the paper setting position to the image forming position in the direction along the tray moving direction.
In such a paper feeder, conventionally, the tray positioning mechanism includes a bent plate-like contact member having a position adjusting plate portion extending in the tray moving direction, and a contact plate-like portion extending in the paper feed direction. The position adjusting plate portion defines a linear slot extending in the tray moving direction. The tray positioning mechanism further includes a bolt-like object passed through the slot and screwed to the paper feed tray or the main apparatus body, to attach the bent plate-like contact member to the paper feed tray or the main apparatus body.
The bolt-like object is loosened to allow the bent plate-like contact member to move along the tray moving direction. The bent plate-like contact member is moved along the tray moving direction, to move the contact portion provided in the contact plate-like portion in the tray moving direction and set the contact portion to a target position. Thereafter the bolt-like object is tightened to the paper feed tray or the main apparatus body, to attach the bent plate-like contact-member to the paper feed tray or the main apparatus body. In this way, the position of the contact portion is varied and adjusted in the tray moving direction, to adjust the optical axis of the image.
In a different conventional construction, the tray positioning mechanism includes a bent plate-like contact member having a position adjusting plate portion extending in the tray moving direction, and a contact plate-like portion extending in the paper feed direction, in which the position adjusting plate portion defines a plurality of bolt receiving bores arranged in the tray moving direction. The tray positioning mechanism further includes a bolt-like object passed through one of the bolt receiving bores and screwed to the paper feed tray or the main apparatus body, to attach the bent plate-like contact member to the paper feed tray or the main apparatus body.
The bolt-like object is removed from the paper feed tray or the main apparatus body, and is passed through a desired one of the bolt receiving bores and tightened to the paper feed tray or the main apparatus body, to attach the bent plate-like contact member to the paper feed tray or the main apparatus body. In this way, the position of the contact portion is varied and adjusted in the tray moving direction, to adjust the optical axis of the image (see Japanese Patent Application “Kokai” No. 2001-287840, for example).
The conventional paper feeders have the following drawbacks in the optical axis adjustment for an image, and improvement has been desired.
In the construction in which the position adjusting plate portion of the bent plate-like contact member defines a linear slot extending in the tray moving direction, and the bolt-like object is passed through the slot and screwed to the paper feed tray or the main apparatus body to attach the bent plate-like contact member to the paper feed tray or the main apparatus body, the bolt-like object is loosened to allow the bent plate-like contact member to move along the tray moving direction without being removed from the paper feed tray or the main apparatus body. This allows the position of the contact portion to be adjusted in the tray moving direction, and the optical axis of an image may be carried out relatively easily.
However, with the bolt-like object passed through an intermediate position with respect to the tray moving direction of the slot, and screwed to the paper feed tray or main apparatus body, when the tray positioning mechanism contacts one of the paper feed tray and the main apparatus body, a force applied to the tray positioning mechanism counter to the tray loading direction (which may be called contact reaction force herein after) is received by a frictional force produced by tightening the bolt-like object to the paper feed tray or main apparatus body. When the tray positioning mechanism is strongly pressed on the paper feed tray or main apparatus body to apply a strong contact reaction force, or when the bolt-like object is tightened only insufficiently, the position of the bent plate-like contact member attached to the paper feed tray or main apparatus body tends to shift in the tray moving direction, and therefore the position of the contact portion also tends to shift. This results in a problem that the adjusted paper setting position tends to deviate from the image forming position.
In the construction in which the position adjusting plate portion of the bent plate-like contact member defines a plurality of bolt receiving bores arranged in the tray moving direction, and a bolt-like object is passed through one of the bolt receiving bores and screwed to the paper feed tray or the main apparatus body to attach the bent plate-like contact member to the paper feed tray or the main apparatus body, a contact reaction force will be received in the state of the bolt-like object contacting the inner peripheral surface of the bolt receiving bore. It is then possible to prevent the position of the bent plate-like contact member attached to the paper feed tray or the main apparatus body from shifting in the tray moving direction. As a result, the optical axis of an image may be adjusted in a way to avoid a deviation the adjusted position of the paper setting position (which may be called simply the adjusted position hereafter) from the image forming position.
However, an operation for adjusting the optic axis of an image must be carried out by once removing the bolt-like object from the paper bed tray or the main apparatus body, passing the bolt-like object through a desired one of the bolt receiving bores and tightening the bolt-like object to the paper feed tray or the main apparatus body. Thus, the optical axis adjusting operation of an image is complicated and troublesome.
This invention has been made having regard to the state of the art noted above, and its object is to provide a paper feeder for an image forming apparatus which can prevent a deviation of an adjusted position by a simple operation to adjust an optical axis of an image.